The proposed research is designed to determine the chemical and structural changes which take place both in the molecular configurations of bone mineral components and in their interactions with the organic components, during nucleation, maturation and aging. These changes occurring in bone as a tissue and as an organ influence the quality of bone fabric as a material (mechanical support) and as an ion reservoir (physiological role). The delineation of those changes in normal tissues will serve as a base line to assess the effect on the qualities of the bone fabric caused by pathological conditions including osteoporosis, osteomalacia, Paget's disease and rickets. To overcome the biological problem due to tissue heterogeneity, we have developed several new preparative procedures, including differential density centrifugation, which yields tissue samples that are homogeneous with respect to the stage of maturation from the earliest deposits, through progressively increasing degrees of mineralization and including the most mature stages reached during aging. To overcome the physical problem caused by deviations of mineral components from crystallographic perfection, we will use a combination of newly developed techniques to probe both short- and long-range atomic order. In addition to the more classical chemical and crystallographic analyses, including their most recent refinements, we will use extended x-ray absorption fine structure analysis (EXAFS) and electron-nuclear double resonance (ENDOR). High resolution nuclear magnetic resonance (NMR) in solid state samples rotating at the magic angle (MASS) will provide a tool of analysis with a resolving power superior to that of conventional diffraction techniques. These analyses will provide a unique description of some of the major structural physical-chemical and biological events in calcification of bone tissues. This project on the temporal changes of the mineral components of bone and the adjacent organic matrix will be coordinated with on-going research activities of this department aimed at determining the spatial location and ultrastructure of mineral components in the tissues.